UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS. 


COLLEGE  OF  AGRICULTURE. 


AGRICULTURAL    EXPERIMENT    STATION. 


SPRAYING  FOR  SCALE  INSECTS 


By  H.  J.  QUAYLE. 


BULLETIN    No.    166. 

(Berkeley,  April,  1905.) 


SACRAMENTO 


w.  w.  shannon,     :     :     :     :     superintendent  state  printing, 

1905. 


BENJAMIN  IDE  WHEELER,  Ph.D.,  LL.D.,  President  of  the  University. 

EXPERIMENT  STATION  STAFF. 

E.  W.  HILGARD,  Ph.D.,  LL.D.,  Director  and  Chemist. 

E.  J.  WICKSON,  M.A.,  Horticulturist. 

W.  A.  SETCHELL,  Ph.D.,  Botanist. 

ELWOOD  MEAD,  M.S.,  C.E.,  Irrigation  Engineer. 

C.  W.  WOODWORTH,  M.S.,  Entomologist. 

R.  H.  LOUGHRIDGE,  Ph.D.,  Agricultural  Geologist  and  Soil  Physicist.    (Soils  and  Alkali.) 

M.  E.  JAFFA,  M.S.,  Assistant  Chemist.    (Foods,  Nutrition.) 

G.  W.  SHAW,  M.A.,  Ph.D.,  Assistant  Chemist.    (Starches,  Oils,  Beet-Sugar.) 

GEORGE  E.  COLBY,  M.S.,  Assistant  Chemist.    (Fruits,  Waters,  Insecticides.) 

RALPH  E.  SMITH,  B.S.,  Plant  Pathologist. 

A.  R.  WARD,  B.S.A.,  D.V.M.,  Veterinarian,  Bacteriologist. 

E.  W.  MAJOR,  B.Agr.,  Animal  Industry. 

A.  V.  STUBENRAUCH,  M.S.,  Assistant  Horticulturist,  in  charge  of  Substations. 

E.  H.  TWIGHT,  B.Sc,  Diplome  E.A.M.,    Viticulturist. 

F.  T.  BIOLETTI,  M.S.,    Viticulturist. 

WARREN  T.  CLARKE,  B.S.,  Assistant  Field  Entomologist. 

H.  M.  HALL,  M.S.,  Assistant  Botanist. 

H.  J.  QUAYLE,  A.B.,  Assistant  Entomologist. 

GEORGE  ROBERTS,  M.S.,  Assistant  Chemist,  in  charge  Fertilizer  Control. 

C.  M.  HARING,  D.V.M.,  Assistant  Veterinarian  and  Bacteriologist. 

0.  A.  COLMORE,  B.S.,  Clerk  to  the  Director. 


R.  E.  MANSELL,  Foreman  of  Central  Station  Grounds. 
JOHN  TUOHY,  Patron, 


J 


,    Tulare  Substation,  Tulare. 
JULIUS  FORRER,  Foreman, 

J.  E.  McCOMAS,  Patron,  Pomona,  n 

J.  W.  MILLS,  Superintendent,  Pomona, 

,      .  „  ..      „         .        ,     ,-     .,         ~  ,.,,       .       >    Southern  California  Substation. 

In  charge  Cooperation  Experiments  of  Southern  California, 

JOHN  H.  BARBER,  Assistant  Superintendent,  Ontario,  J 

J.  W.  ROPER,  Patron,  )    „    . 

ttt7.xtt>^  ™rT^TT™TAXT    t      i.  C  University  Forestry  Station,  Chico. 

HENRY  WIGHTMAN,  In  charge,      ) 

ROY  JONES,  Patron, 

WM.  SHUTT,  Foreman, 

H.  O.  WOODWORTH,  M.S.,  Foreman  of  Poultry  Station,  Petaluma. 


V  University  Forestry  Station,  Santa  Monica. 


The  Station  publications  (Reports  and  Bulletins),  so  long  as  avail- 
able, will  be  sent  to  any  citizen  of  the  State  on  application. 


CONTENTS. 


Page. 

INTRODUCTION 5 

THE  LIME-SULFUR-SALT  WASH 5 

History  in  California  :  History  in  the  East 5 

Kings  County  experiments 7 

Experiments  in  dilutions  ;  Difference  in  amount  of  lime  ;  Difference  in  amount 
of  sulfur ;  Difference  in  amount  of  salt ;  Bluestone  instead  of  salt ;  Making  a 
lime-sulfur-salt  wash  without  boiling ;  How  wash  affects  the  scales  ;  Effect  on 

the  tree 7 

SUGGESTIONS  FOR  LIME-SULFUR-SALT  WASH 12 

The  formula;  Preparation;  Application 12 

REMEDIES  FOR  THE  BROWN  APRICOT  SCALE 15 

Inefficiency  of  the  lime-sulfur-salt  wash 15 

THE  RESIN  COMPOUND 15 

Experiments  in  dilutions ;  The  use  of  resin ;  Use  of  fish  oil ;  Addition  of  arsenic ; 
Character  of  wash  ;  Effect  on  the  scales ;  Effect  on  the  tree ;  Preparing  a  wash 

without  boiling 18 

SUGGESTIONS  FOR  RESIN  SPRAY  _. 19 

The  formula;  Preparation;  Ingredients  and  cost ;  Application 20 

THE  DISTILLATE  SPRAY 21 

Increase  in  amount  of  oil ;  Addition  of  potash  ;  Effect  of  the  distillate  spray 21 

SUGGESTIONS  FOR  DISTILLATE  SPRAY 22 

PATENT  COMPOUNDS 23 

I  X  L;  I  X  L  and  Resin  Compound  compared;  Fruitolin  ;  The  carbolic  spray 23 

RESUME 24 


SPRAYING  FOR  SCALE  INSECTS. 

By  H.  J.  QUAYLE. 


Introduction. — The  experiments  recorded  in  this  bulletin  were  con- 
ducted by  the  Experiment  Station  in  cooperation  with  the  Kings  County- 
Board  of  Horticulture  and  with  the  fruit-growers  in  the  neighborhood 
of  Hanford.  The  work  included  spraying  operations  against  the  two 
most  important  scale  insects  of  the  county,  namely,  the  brown  apricot 
and  San  Jose  scales. 

The  brown  apricot  scale  (Eulecanium  armeniacum,  Craw)  has  been 
known  to  occur  in  California  since  1891,  but  it  is  said  to  have  been 
unknown  as  a  pest  in  Kings  County  until  within  the  last  three  or  four 
years.  It  is  now,  however,  widely  distributed  throughout  the  county, 
and  is  the  most  important  scale  insect  with  which  the  orchardist  has 
to  deal.  While  the  popular  name  of  this  insect  is  the  brown  apricot 
scale,  it  is  not  upon  the  apricot  tree  that  it  thrives  best,  but  instead 
shows  a  decided  preference  for  the  prune,  and  it  is  upon  this  tree  that 
it  does  the  most  serious  injury. 

Next  in  importance  to  the  brown  apricot  scale  is  the  well-known  San 
Jose  scale.  This  insect  is  not  so  uniformly  distributed  over  the  county, 
and  occurs  in  serious  numbers  only  in  limited  areas,  seldom  an  entire 
orchard  being  completely  infested.  While  the  San  Jose  scale  attacks  a 
great  variety  of  trees,  it  particularly  delights  in  the  apple  and  pear  in 
that  section,  and  there  are  few  old  apple  or  pear  trees  in  the  county, 
which  have  escaped  treatment,  that  are  free  from  infestation  of  this  scale. 

Heretofore  the  remedies  applied  for  the  brown  apricot  scale  seemed 
to  have  been  inadequate  to  keep  it  under  proper  control,  and  it  was  the 
purpose  of  these  experiments  to  determine  upon  an  effective  remedy  for 
this  insect,  as  well  as  to  decide  upon  a  satisfactory  formula  for  the  lime- 
sulfur-salt  wash,  which  is  the  standard  remedy  for  the  San  Jose  scale. 
The  work  was  done  in  Kings  County  in  the  upper  San  Joaquin  Valley 
in  the  immediate  vicinity  of  Hanford,  and  included  the  spraying  of 
about  one  thousand  acres  of  trees,  of  which  the  greater  number  were 
prune,  and  the  balance  consisted  chiefly  of  peach  and  apricot. 

THE    LIME-SULFUR-SALT    WASH. 

History  in  California. — The  lime-sulfur-salt  wash  is  of  California 
origin,  and  in  the  East  it  is  sometimes  known  as  the  California  wash. 
The  above  ingredients  with  water  originally  constituted  a  sheep  dip,  and 


6  UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 

when  horticultural  interests  began  to  be  menaced  by  the  ravages  of  the 
San  Jose  scale  it  was  one  of  the  first  mixtures  that  proved  effective  as  a 
remedy.  The  value  of  this  solution  as  a  spray  was  first  demonstrated 
in  1886  by  Mr.  F.  Dusey,  a  resident  of  Fresno,  who  experimented  with 
a  sheep  dip  prepared  by  Mr.  A.  T.  Covell.  The  mixture,  with  some 
modification,  quickly  came  into  favor,  and  is  now  considered  the 
standard  remedy  for  the  San  Jose  scale,  not  only  in  California  but  in 
most  of  the  Eastern  States. 

The  proportion  of  materials  used  in  the  original  experiment  was  : 
lime  80  pounds,  sulfur  100  pounds,  sugar  20  pounds,  salt  10  pounds,  and 
water  160  gallons,  the  whole  being  boiled  for  a  half  hour.  This  was 
originally  prepared,  as  stated  above,  for  a  sheep  dip,  and  a  small 
quantity  was  applied  to  some  trees  near  by  that  were  infested  with  the 
San  Jose  scale.  In  subsequent  experiments  the  amounts  of  materials 
were  changed  considerably,  and  the  first  formulas  recorded  for  a  tree 
spray  are  those  recommended  by  Mr.  I.  H.  Thomas  and  Mr.  A.  T.  Covell 
in  the  report  of  the  California  State  Board  of  Horticulture  for  1887-88. 
A  few  years  later,  in  1890,  Mr.  Thomas  advocated  the  strengthening  of 
his  first  formula  by  the  increase  of  five  pounds  each  of  lime  and  sulfur. 
In  the  following  year  the  amount  of  lime  was  increased  and  the  amount 
of  sulfur  decreased,  as  shown  in  the  formula  which  appeared  in 
Mr.  Lelong's  report,  as  Secretary  of  the  State  Board  of  Horticulture, 
for  1891.  At  about  the  same  time  the  Horticultural  Commissioners  of 
Sutter  County  did  some  further  work  with  the  wash,  but  finally 
adopted  the  same  formula  as  that  given  in  the  report  for  1891.  This 
formula,  up  to  the  present  time,  has  been  considered  the  standard  in 
this  State. 

The  following  tabulation  shows  the  evolution  of  the  wash  in  Cali- 
fornia: 

Lime,  Sulfur,  Salt,  Sugar,  Water, 

lbs.  lbs.  lbs.  lbs.  gals. 

1886,  Original  formula  (sheep  dip) 80  100  10  20  160 

1887,  I.  H.  Thomas 25  20  15  ..  60 

1887,  A.  T.  Covell 50  20  15  ..  60 

1890,  I.  H.  Thomas 30  25  15  ..  60 

1891,  Lelong's  report 40  20  15  ._  60 

Hort.  Com.  Sutter  County 40  20  15  -  60 

1904,  Recommended  in  this  bulletin 30  15  10  ..  60 

History  in  the  East. — The  lime-sulfur-salt  wash  was  slow  in  getting  a 
place  among  the  standard  remedies  in  the  East.  In  1895  Marlatt  and 
Coquillett  gave  the  wash  a  practical  test  under  Eastern  conditions, 
and  the  results  were  so  unsatisfactory  that  its  use  was  abandoned  until 
it  was  again  tried  by  Marlatt  in  1900.  The  second  attempt  proved 
more  successful  than  the  first,  and  in  fact  gave  gratifying  results,  and 
it  is  from  this  date  that  the  lime-sulfur-salt  wash  rapidly  came  into  use 
in  the  East.     The  failure  of  the  first  experiment   under  Eastern  con- 


SPRAYING    FOR    SCALE    INSECTS.  7 

ditions  is  attributed  to  the  fact  that  the  application  was  followed  by  a 
period  of  drenching  rains,  a  condition  which  has  not  entered  so  largely 
into  the  California  experience;  while  in  the  second  case  a  period  of  dry 
weather  followed  the  application  of  the  spray,  and  the  results  proved 
more  favorable. 

This  wash  was  further  tested  during  the  winter  of  1901-02  by  Pro- 
fessor Forbes,  of  Illinois,  with  the  result  that  it  was  satisfactory,  even 
if  the  application  was  followed  by  a  reasonable  amount  of  rainfall. 
During  the  past  two  or  three  years  extensive  experiments  have  been 
carried  on  with  the  wash  in  many  of  the  Eastern  States,  prominent 
among  which  are  the  stations  of  New  York,  New  Jersey,  Connecticut, 
Delaware,  Virginia,  Georgia,  Ohio,  Kentucky,  and  Illinois.  The  gen- 
eral verdict  of  these  experiments  has  been  the  adoption  of  the  lime- 
sulfur-salt  wash  as  a  remedy  for  the  San  Jose  scale. 

The  formula  recommended  by  the  different  States  at  the  East  is 
shown  in  the  following  table:    . 

Lime.  Sulfur,  Salt,  Water,  Time 

lbs.  lbs.  lbs.  gals.  Cooked. 

U.  S.  Dept.,  Washington 40  20  15  60  2    hrs. 

New  Jersey 50  50  50  150  1^  hrs. 

Maryland 40  20  15  60  2    hrs. 

Georgia 30  20  15  60  2^-3    hrs. 

Illinois 15  15  15  50  1J  hrs. 

New  York  (Geneva)... 40  20  15  60  2-2|  hrs. 

Kentucky I 20  14  10  40  1^  hrs. 

Connecticut 20  14  10  40  1J  hrs. 

Virginia 30  30  10  100  30-40  min. 

Ohio  15  15  15  50  1J  hrs. 

Delaware 5  5  5  15  1^  hrs. 

KINGS    COUNTY    EXPERIMENTS. 

While  the  formula  adopted  in  1891  has  proved  to  be  satisfactory 
from  the  point  of  view  of  results,  yet  there  lacked  work  of  an  experi- 
mental character  to  determine  whether  or  not  the  materials  were  used 
in  the  proper  proportion  consistent  with  the  best  results  and  at  the 
least  cost.  It  was  with  a  view,  primarily,  to  determine  this  that  the 
following  experiments  were  undertaken. 

The  field  of  operations  included  several  hundred  acres,  the  main 
work,  however,  being  done  on  a  single  orchard  of  240  acres.  This 
orchard  included  about  200  acres  of  prune  trees  and  40  acres  of  peach 
trees.  The  San  Jose  scale  was  unevenly  distributed  over  the  orchard, 
varying  from  badly  infested  localities  to  places  that  were  entirely  free. 
The  spraying  was  done  mostly  during  February  and  March,  a  period 
during  which  but  little  rain  fell. 

Experiments  in  Dilutions. — Since  the  old  formula  40,  20,  15,  60,  of 
lime,  sulfur,  salt,  and  water  respectively,  when  properly  prepared  and 
applied,  gave  favorable  results,  the  first  work  done  was  with  dilutions 


8  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

of  this  formula  with  a  view  to  cheapening  the  cost  if  possible.  With 
the  above  formula  as  a  standard,  the  amount  of  water  was  increased  by 
10  gallons  at  a  time  until  double  the  amount  of  water,  or  120  gallons, 
was  used.  A  considerable  number  of  trees,  varying  from  100  to  700, 
were  sprayed  with  each  of  the  dilutions,  so  that  the  results  might  be 
judged  from  a  practical  test  rather  than  from  laboratory  experiments. 
While  the  results  of  such  large-scale  tests  can  not  be  stated  by  a  definite 
number  of  scales  killed,  or  not  killed,  yet  it  is  believed  that  this 
method  is  preferable  as  a  basis  for  recommendation  to  the  practical 
orchardist.  As  supplementary  to  these  tests,  laboratory  experiments 
on  a  few  twigs  were  carried  on  as  a  check  to  the  larger  experiments. 
The  results  of  these  experiments  are  given  in  the  tables  which  follow: 

TABLE  No.   1. 

Lime,  Sulfur,  Salt,  Water, 

No.  of  Trees.  lbs.  lbs.  lbs.  gals.  Result. 

700 40  20  15  60  No  scales  alive. 

300 40  20  15  70  No  scales  alive. 

700 40  20  15  80  No  scales  alive. 

300 40  20  15  90  No  scales  alive. 

200--- «  20  15  100  |A^TSl!liTe 

100 40  20  15  120  Several  alive. 

TABLE  No.  2. 

Lime,  Sulfur,  Salt,  Water, 

Scales  on  Twigs.  lbs.  lbs.  lbs.  gals.  Result. 

400 40  20  15  60  All  killed. 

250 40  20  15  70  Two  alive. 

320 40  20  15  80  All  killed. 

290 40  20  15  90  All  killed. 

210 40  20  15  100  All  killed. 

200 40  20  15  120  Eleven  alive. 

During  the  experiments  recorded  in  Table  No.  1,  there  were  no 
drenching  rains  and  nothing  to  disturb  the  wash  upon  the  trees  beyond 
a  few  gentle  showers.  Of  course,  the  examination  on  such  a  large  scale 
was  not  searching  enough  in  the  case  of  each  tree  to  examine  every 
scale,  but  simply  a  careful  examination  of  the  entire  lot. 

In  Table  No.  2  the  twigs  were  examined  beforehand  to  determine  the 
per  cent  of  scales  already  dead,  and  this  was  found  to  average  60  per 
cent  for  the  entire  number.  The  twigs  were  then  thoroughly  sprayed, 
or  in  some  cases  a  marked-off  portion  of  the  trunk,  or  large  limb,  and 
the  final  examination  made  five  weeks  later. 

From  these  tests  it  would  appear  that  the  old  formula  may  be  reduced 
somewhat,  with  no  serious  difference  in  the  results.  While  the  formula 
including  100  gallons  of  water  gave  good  results,  yet  it  was  due  in  part 
probably  to  the  thoroughness  of  application,  so  that  it  had  the  effect  of 
a  stronger  solution.  In  ordinary  work,  therefore,  it  would  not  be  safe 
to  recommend  a  greater  dilution  than  80  gallons. 


SPRAYING   FOR    SCALE    INSECTS.  9 

Difference  in  Amount  of  Lime. — Various  amounts  of  lime  were  used, 
ranging  from  20  to  50  pounds,  as  given  in  the  formulas  below: 


Ame, 

Sulfur, 

Salt, 

Water, 

lbs. 

lbs. 

lbs. 

gals. 

Effect. 

50 

20 

15 

60 

All  killed. 

45 

20 

15 

60 

All  killed. 

40 

20 

15 

60 

All  killed. 

35 

20 

15 

60 

All  killed. 

30 

20 

15 

60 

All  killed. 

20 

20 

15 

60 

All  killed. 

The  amount  of  lime  necessary  to  combine  with  the  sulfur  has  been 
found  by  practical  tests  to  be  about  equal  parts  by  weight,  and  for  this 
reason  equal  amounts  only  are  recommended  by  some  stations,  some 
going  so  far  as  to  say  that  an  excess  of  lime  amounts  to  mere  white- 
wash. The  combination  effected  between  the  lime  and  sulfur  is  not  a 
simple  one,  however,  and  it  may  be  that  the  different  compounds  pro- 
duced, when  different  proportions  of  lime  are  present,  may  make  an 
essential  difference  in  the  effectiveness  of  the  wash.  These  experi- 
ments were  not  full  enough  to  give  any  very  definite  data  upon  this 
point,  but  that  there  is  some  effect,  apparently  due  to  the  mere  presence 
of  uncombined  lime,  is  shown  by  the  difference  noted  during  the  appli- 
cation of  a  single  tankful,  due  to  its  settling  from  lack  of  proper 
agitation.  It  was  found  that  the  live  scales,  if  any,  were  more  abun- 
dant where  there  had  been  a  scarcity  of  lime.  Particularly  is  this  true 
where  heavy  rains  will  readily  wash  away  the  clear  liquid  and  reduce 
the  period  of  effectiveness.  A  comparative  experiment  showing  the 
effect  of  the  clear  liquid,  and  one  in  which  there  was  a  considerable 
excess  of  lime,  follows.  The  clear  liquid  was  that  which  remained  at 
the  top  after  the  wash  was  allowed  to  settle  for  twenty-four  hours. 

No.  Scales    Number    Number       Dead,         Alive, 
Counted.       Dead.        Alive.       per  cent,    per  cent. 

Clear  liquid 512  482  30  94.1  5.9 

Excess  of  lime 340  340  0  100.0  0.0 

It  is  a  common  opinion  now  that  the  less  easily  soluble  compounds 
remain  effective  for  some  time,  and  these  are  better  retained  in  the 
coating  formed  by  the  lime.*  On  the  other  hand,  too  much  lime  is 
unnecessary,  especially  when  it  is  applied  by  a  hand  pump  with  no 

*  According  to  the  analysis  made  by  Mr.  Fuller  of  the  New  York  station,  the  following 
lime  compounds  are  formed :  Calcium  sulfid  (CaS),  some  of  the  polysulfids  of  calcium 
(CaS3  and  CaS5),  calcium  sulfate  (CaS04),  a  large  quantity  of  calcium  thiosulfate 
(CaS203),  and  some  calcium  sulfite  (CaS03).  If  equal  amounts  of  these  different  com- 
pounds were  formed,  then  according  to  the  atomic  weights  there  would  be  a  greater 
amount  of  sulfur  than  of  lime  (1  part  of  lime  to  2.285  parts  of  sulfur);  but  since  the 
relative  amounts  of  these  compounds  have  not  been  determined,  we  can  not  say 
whether  the  sulfur  and  lime  combine  equally  by  weight  or  whether  there  is  not  an 
excess  of  one  over  the  other.  It  was  not  the  purpose  of  these  experiments  to  study  the 
wash  from  a  chemical  standpoint,  but  much  might  be  done  along  this  line. 


10  UNIVERSITY    OF   CALIFORNIA — EXPERIMENT   STATION. 

apparatus  to  keep  the  lime  in  suspension,  since  the  lime  quickly  settles 
to  the  bottom,  where  it  is  taken  up  by  the  pump  and  applied  on  the 
first  few  trees. 

Variation  in  Amount  of  Sulfur. — We  may  consider  sulfur  as  the 
important  ingredient  of  the  wash,  since  it  is  the  compounds  formed  by 
the  union  with  the  lime  that  gives  it  its  principal  insecticidal  value. 
All  the  sulfur  will  enter  into  combination  so  long  as  there  is,  approxi- 
mately, an  equal  amount  of  lime  to  combine  with  it.  The  sulfur, 
therefore,  may  be  called  the  basic  ingredient  of  the  wash,  and  the  pro- 
portion of  this  substance  present  determines  the  strength  of  the  wash, 
providing  there  is  the  necessary  amount  of  lime  present. 

Different  amounts  of  sulfur  were  tried,  the  quantities  varying  from 
40  to  50  pounds  to  each  60  gallons  of  water.  A  material  reduction  in 
the  amount  of  sulfur  changed  the  character  of  the  wash  both  as  to 
color  and  specific  gravity.  The  effect  of  the  solutions  containing  a 
small  amount  of  sulfur  on  the  scales  was  a  falling  off  in  efficiency. 


Lime, 
lbs. 

Sulfur, 

lbs. 

Salt, 
lbs. 

Water, 
gals. 

Effect  on  Scales. 

40 

40 

15 

GO 

Good. 

40 

35 

15 

60 

Good. 

40 

30 

15 

60 

Good. 

40 

20 

15 

60 

Good. 

40 
40 

10 
5 

15 
15 

60 
60 

Not  satisfactory. 
Not  satisfactory. 

Difference  in  Amount  of  Salt. — The  use  of  salt  in  the  lime-sulfur-salt 
wash  is  still  a  mooted  question,  some  advocating  the  doing  away  with 
the  salt  entirely,  while  others  still  use  it,  with  its  exact  function  a 
questionable  point.  While  in  these  experiments  several  hundred  trees 
sprayed  without  the  salt  gave  no  difference  in  the  results  that  was 
discernible,  yet  we  are  not  ready  to  recommend  its  disuse. 

What  has  been  claimed  for  the  salt  is: 

(1)  That  it  raises  the  boiling  point  of  the  wash,  and  thus  insures  a 
better  union  between  the  lime  and  sulfur. 

(2)  That  it  adds  to  the  adhesive  qualities  of  the  wash. 

(3)  That  it  renders  the  precipitate  more  flocculent,  that  is,  the 
heavier  materials  remain  in  suspension  better,  and  occupy  more  space 
in  the  lighter  liquid. 

In  addition  to  this  the  hygroscopic  behavior  of  the  salt,  or  power  to 
absorb  water,  may  insure  the  gradual  solution  of  the  less  easily  soluble 
compounds.  It  is  probable  also,  that  the  salt  adds  to  the  penetrating 
power  of  the  wash,  if  this  may  be  separated  from  the  hygroscopic  action, 
and  makes  the  solution  more  effective  on  badly  incrusted  trees. 

Bluestone  instead  of  Salt. — The  experiments  with  bluestone  consisted 
in  the  treatment  of  but  200  trees,  and  on  account  of  a  high  wind  at  the 


SPRAYING   FOR    SCALE    INSECTS.  11 

time  the  wash  was  prepared,  the  application  was  delayed  until  the  fol- 
lowing day,  and  consequently  the  wash  was  applied  cold.  There  was 
■a  very  heavy  precipitate,  and  it  required  constant  stirring  to  keep  it  in 
suspension.  The  trees  were  examined  two  months  later,  with  the  result 
that  live  scales  were  not  uncommon.  The  bluestone  was  effective  in 
cleaning  the  moss  from  the  tree,  but  beyond  this  its  advantages  in  the 
wash  were  not  apparent. 

Making  a  Lime-Sulfur- Salt  Wash  without  Boiling. — The  trouble  and 
expense  of  boiling  have  been  the  chief  objections  to  the  use  of  this 
wash,  and  it  was  with  a  view  to  overcoming  this  difficulty  that  the 
New  York  station  originated  a  method  of  cooking  the  wash  without  the 
use  of  fire.  To  do  this,  caustic  soda  was  added  to  dissolve  the  sulfur, 
and  the  same  combination  with  the  lime  is  supposed  to  take  place.  The 
amount  of  caustic  soda  (76  per  cent)  required  is  1  pound  to  every  2  or 
3  pounds  of  sulfur.  One  pound  to  more  than  three  of  sulfur  did  not 
give  satisfactory  results. 

To  prepare  the  wash  according  to  this  method,  the  sulfur  was  sifted 
through  mosquito  wire-netting  into  two  or  three  inches  of  water  in  the 
boiler,  and  stirred  in  thoroughly,  when  the  lime  was  added,  about  one 
fourth  of  the  total  amount  at  a  time.  When  the  lime  was  well  slaked 
the  caustic  soda  was  added,  a  portion  at  a  time,  in  the  same  way  in 
which  the  lime  was  added.  The  mixture  was  kept  well  stirred  and  was 
ready  for  use  in  about  twenty  minutes.  Hot  water  was  added  by 
preference. 

About  500  trees,  which  were  but  very  slightly  infested  with  the  San 
Jose  scale,  were  treated  with  the  wash  prepared  in  this  way.  The  few 
scales  that  were  present  seemed  to  be  killed.  The  effect  on  the  brown 
apricot  scale  was  the  same  as  that  of  the  regular  wash,  namely,  that  a 
large  number  remained  unharmed. 

The  wash  prepared  in  this  way,  however,  has  not,  according  to  the 
present  experience,  overcome  the  objections  for  which  the  method  was 
proposed. 

A  comparison  in  the  cost  of  the  two  methods  as  involved  in  a  day's 
work  with  a  power  outfit,  applying  a  total  of  2,000  gallons,  is  as  follows: 

Table  Showing  Difference  in  Cost  of  the  Two  Methods. 
Boiling  by  Fire.  Caustic  Soda  Method. 

1,000  lbs.  lime,  at  2  cents $20  00  1,000  lbs.  lime,  at  2  cents $20  00 

500  lbs.  sulfur,  at  2|  cents 13  75  500  lbs.  sulfur,  at  2|  cents 13  75 

330  lbs.  salt,  at  h  cent 1  65  200  lbs.  caustic  soda,  at  6  cents..  12  00 


Total $35  40  Total $45  75 

This  leaves  a  balance  of  $10  at  the  end  of  each  day  in  favor  of  the 
old  method.  Granting  that  it  requires  an  extra  man,  the  wages  and 
fuel  together  should  not  go  above  $5,  which  still  leaves  a  balance  of  $5 


12  UNIVERSITY    OF   CALIFORNIA — EXPERIMENT   STATION. 

in  favor  of  the  old  method.  This  does  not  take  into  consideration  the 
fact  that  the  recommendations  for  the  soda  method  call  for  hot  water, 
which  likewise  requires  fuel  as  well  as  labor. 

This  wash  is  still  in  the  experimental  stage,  so  far  as  the  effect  on 
the  insects  is  concerned,  it  proving  effective  in  some  cases  and  ineffect- 
ive in  others.  The  conditions  governing  this  difference  in  results  have 
not  yet  been  determined. 

If,  by  further  experimentation,  the  results  can  be  made  more  uniform, 
this  method  of  preparing  the  wash  will  prove  useful  on  a  small  scale 
and  where  apparatus  for  boiling  is  not  at  hand. 

The  Effect  the  Wash  Has  on  the  Scales. — The  wash  evidently  kills  the 
scales  by  contact,  and  this  is  supposed  to  be  due  to  its  caustic  effect. 
The  easily  soluble  compounds  act  upon  the  scales  immediately,  while 
the  less  soluble  compounds  remain  effective  for  some  little  time.  In 
addition  to  this,  the  mechanical  effect  due  to  the  coating  of  the  lime 
may  possibly  prevent  the  escape  of  the  young. 

Effect  on  the  Tree. — The  wash  has  no  appreciable  injurious  effect  on 
the  tree;  that  is,  unless  applied  late  in  the  season  when  the  trees  are 
in  full  bloom.  Even  then,  certain  trees  do  not.  appear  to  suffer,  as 
shown  in  the  case  of  a  number  of  peach  trees  that  were  sprayed  at 
this  period  with  apparently  no  ill  effect.  A  number  of  prune  trees 
were  also  sprayed  while  in  full  bloom,  and  while  the  petals  were  con- 
siderably browned,  the  fruit  suffered  no  serious  injury.  Spraying  at 
this  season,  however,  is  not  to  be  recommended,  since  work  against 
scale  insects  on  deciduous  trees  can  be  accomplished  while  the  tree  is 
still  dormant. 

SUGGESTIONS    FOR    LIME-SULFUR-SALT   WASH. 

The  Formula. — The   formula  determined  upon   as   a  result  of  these 

experiments  which  seemed  most  satisfactory  from  the  point  of  view  of 

cost  and  effectiveness  is  as  folic ws: 

Lime  __.  30  pounds. 

Sulfur 20  pounds. 

Salt , 10  pounds. 

Water 60  gallons. 

Preparation. — For  preparing  the  wash  two  vats  or  boilers  are  neces- 
sary, and  if  the  spraying  is  to  be  done  on  a  large  scale,  one  of  these  at 
least  should  hold  a  couple  of  hundred  gallons.  If  but  a  small  number 
of  trees  are  to  be  treated,  ordinary  iron  kettles  will  answer  the  purpose. 
Of  course,  the  preferable  way  of  cooking  the  wash  is  by  means  of  live 
steam. 

Many  ways  have  been  suggested  for  mixing  the  materials,  but  the 
results  are  the  same  in  every  case,  so  long  as  the  mixture  has  been  sub- 
jected to  the  required  amount  of  boiling.     It  is  largely  a  matter  of  con- 


SPRAYING    FOR    SCALE    INShCTS.  IB 

venience,  then,  that  determines  the  particular  method,  and  the  one 
found  in  these  experiments  to  best  answer  this  requirement  is  as  follows: 
First  place  two  or  three  inches  of  water  in  the  boiler,  and  to  this  add 
the  sulfur,  which  has  previously  been  made  into  a  paste  by  mixing 
with  hot  water  in  order  to  remove  the  lumps,  or  sift  the  dry  sulfur 
through  a  mosquito  wire-netting  and  stir  in  thoroughly.  Then  add 
about  one  fourth  of  the  lime,  and  when  the  violent  boiling  has  ceased 
add  another  fourth,  and  so  on  until  the  required  amount  of  lime  has 
been  added.  Hot  water  should  be  added  with  the  lime  as  needed,  so 
as  to  make  the  mixture  of  a  creamy  consistency.     Too  much  water  will 


Fig.  1.    Preparing  the  wash  on  a  small  scale. 

"drown"  the  lime,  while  on  the  other  hand  too  little  will  cause  incom- 
plete slaking  of  the  lime.  In  this  way  the  heat  generated  by  the 
slaking  of  the  lime  is  taken  advantage  of,  and  by  adding  the  sulfur 
first  plenty  of  time  is  given  for  removing  the  lumps. 

By  the  time  the  lime  is  thoroughly  slaked  the  fire  should  continue 
the  boiling,  so  that  the  time  of  boiling  begins  with  the  addition  of  the 
lime.  The  salt  and  about  one  fourth  of  the  water  should  now  be  added, 
and  the  whole  boiled  from  one  to  two  hours,  keeping  it  frequently 
stirred  in  the  meantime.  At  the  end  of  this  period  screen  into  the 
spray  tank  and  add  the  necessary  amount  of  hot  water  and  apply  to 
the  trees  hot. 

The  wash  when  properly  made  is  a  heavy  reddish-brown  liquid,  very 


14 


UNIVERSITY    OF   CALIFORNIA  — EXPERIMENT    STATION. 


caustic  and  having  a  strong  sulfur  odor.     The  heavier  materials  settle 
upon  standing,  leaving  a  lighter  liquid  both  in  color  and  weight. 

In  order  to  save  fuel,  a  stock  solution  is  recommended.  This  stock 
solution  should  not  be  made  too  concentrated,  on  account  of  the  dif- 
ficulty in  handling  the  heavy  materials  in  the  boiler;  but  an  amount 
sufficient  to  fill  the  spray  tank  two  or  three  times  may  be  made  without 
difficulty.  To  do  this,  say  for  two  tankfuls,  double  the  amounts  of 
materials  used  for  one,  and  put  half  of  the  stock  solution  in  the  spray 
tank  and  fill  up  with  hot  water  as  before.  The  stock  solution  should 
be  well  stirred  while  being  added  to  the  spray  tank,  in  order  that  the 
next  tankful  will  be  of  the  same  strength.     In  this  way  a  considerable 


iffi%*ww>-,J 


Fig.  2.    A  common  outfit  in  California  for  cooking  the  wash. 

amount  of  boiling  is  saved,  and  this  is  an  important  item  if  the  spray- 
ing work  is  extensive. 

Application. — On  account  of  the  heavier  ingredients  of  the  wash 
quickly  settling  to  the  bottom,  means  should  be  provided  for  agitating 
the  mixture  in  the  spray  tank.  This  is  best  done,  of  course,  by  the 
power  outfit.  In  the  absence  of  this,  a  gearing  may  be  attached  to  the 
wheel  of  the  wagon  and  the  mixture  agitated  while  going  from  one  tree 
to  another.  A  still  simpler  way  is  to  stir  frequently  by  means  of  a  hoe 
or  paddle. 

The  nozzle  should  be  of  the  stopcock  type,  which  will  permit  of  ready 
cleaning.  The  type  of  spray  should  be  a  rather  coarse  one  which  will 
thoroughly  wet  the  insects,  and  not  a  fine  mist  as  used  in  paris  green 
work.  Thoroughness  of  application  can  not  be  too  strongly  urged,  and 
no  part  of  the  tree  should  escape  treatment. 


SPRAYING    FOR    SCALE    INSECTS.  15 

REMEDIES    FOR    THE    BROWN    APRICOT    SCALE. 

Inefficiency  of  the  Lime -Sulfur -Salt  Wash. — It  was  the  general  opinion 
among  the  growers  of  Kings  County,  as  elsewhere,  that  the  lime-sulfur- 
salt  wash  was  not  an  effective  remedy  for  the  brown  apricot  scale,  and 
this  opinion  was  verified  during  the  experiments  there  this  season. 

Since  this  wash  has  been  so  often  demonstrated  as  being  efficient  for 
the  control  of  the  San  Jose  scale,  it  seemed  natural  to  infer  that  it 
would  be  equally  satisfactory  as  a  remedy  for  a  naked  scale,  such  as 
the  brown  apricot.  In  consequence,  it  is  continually  being  tried  as  a 
remedy  for  this  insect.  While  the  apricot  scale  lacks  the  protective, 
waxy  covering  with  which  the  San  Jose  scale  is  provided,  yet  because 
of  the  hard,  leathery  texture  of  the  body  of  the  adult  insect,  it  is  almost 
entirely  resistant  to  the  lime-sulfur-salt  mixture.  In  the  case  of  the 
young  insect,  while  it  has  not  yet  attained  the  firm  body-covering  char- 
acteristic of  the  adult,  it  is,  even  in  this  stage,  fairly  resistant  to  insecti- 
cides, evidently  because  of  the  oily  nature  of  the  body  surface.  It  was 
not  uncommon  to  find  the  young  insects  in  the  midst  of  a  heavy  coating 
of  the  wash,  but  none  of  it  adhered  to  the  insect  itself.  Very  often  it 
was  observed  that  the  scales  were  covered  over  with  the  wash  directly 
after  the  application,  but  that  they  had  the  power,  later,  of  throwing  off 
this  covering  or  loosening  it  to  such  an  extent  that  rains  or  other  causes 
finally  removed  it,  leaving  the  insect  free. 

From  these  observations  it  became  evident  at  once  that  the  spray 
could  be  only  partially  effective  against  the  apricot  scale,  and  this  con- 
clusion was  further  verified  by  the  following  experiment.  Twigs  were 
sprayed  February  15th  and  examined  March  12th: 

Table  Showing  Effect  of  Lime-Sulfur-Salt  Wash  on  Brown  Apricot  Scale. 

Alive,  Dead, 

Twig.                                                No.  Scales.  Alive.  Dead.  per  cent.  per  cent. 

1 30                    12  18  40  60 

2 52                   18  34.  35—  65+ 

3- 38                     8  30  21+  79— 

4 44                   14  30  31+  69+ 

5 63                   28  35  44—  66+ 

6 62                   16  46  25+  75— 

Totals 289  96  193  33+  67+ 

THE   RESIN    COMPOUND. 

The  failure  of  the  lime-sulfur-salt  wash  to  control  the  brown  apricot 
scale  led  to  the  use  of  the  resin  compound  as  a  remedy  for  this  insect. 

The  resin  compound  was  first  used  by  Mr.  Albert  Koebele  in  1886, 
and  was  first  applied  in  the  southern  part  of  this  State  as  a  remedy  for 
the  cottony  cushion  scale.  It  came  into  quite  general  favor,  and  has 
been  used  more  or  less  since  as  a  remedy  for  scale  insects  in  California. 


16  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

In  the  Eastern  States,  however,  it  has  never  come  into  very  general 
use,  and  this  is  possibly  due  to  the  climatic  conditions  prevailing  there 
which  might  make  it  less  likely  to  adhere  to  the  tree  long  enough  to  be 
effective. 

In  the  present  experiments  the  compound  was  applied  to  about  6,000 
prune  trees  that  were  thoroughly  infested  with  the  brown  apricot  scale, 
and  some  of  these  were  also  slightly  attacked  by  the  San  Jose  scale. 
The  spraying  was  started  on  the  17th  of  February  and  continued  until 
the  21st  of  March,  when  the  trees  were  almost  in  full  bloom.  The  time 
of  application  was  delayed  longer  than  our  present  experience  would 
warrant,  since  spraying  so  late  as  the  middle  of  March,  at  least  in  the 
upper  San  Joaquin  Valley,  is  not  only  less  effective  on  the  apricot 
scale,  but,  in  the  case  of  such  a  strong  wash  as  the  resin  compound,  it 
is  also  likely  to  do  injury  to  the  tree. 

Experiments  in  Dilutions. — The  formula  for  the  resin  compound 
which  has  been  generally  recommended  for  winter  use  on  deciduous 
trees  in  this  State  was: 

Resin 12    pounds. 

Caustic  soda  (76%) 3    pounds. 

Fish  oil 1^  pounds. 

Water 40    gallons. 

The  work  had  not  progressed  far  until  it  was  found  that  the  resin 
compound  killed  the  brown  apricot  scale  very  effectively,  so  the  first 
experiments  were  along  the  line  of  dilution,  in  order  to  determine  if  a 
weaker  mixture  would  not  give  the  same  results.  In  the  first  experi- 
ment the  water  was  increased  to  50  gallons,  instead  of  40,  as  given  in 
the  standard  formula.  This  solution  was  applied  very  thoroughly  to 
200  trees,  and  seemed  just  as  effective  as  the  normal  solution.  The 
water  was  then  increased  to  60  gallons,  and  a  considerable  number  of 
trees  sprayed  with  this  strength.  Here,  too,  the  results  were  quite  sat- 
isfactory, but  there  was  a  noticeable  difference  in  the  character  of  the 
wash,  it  being  a  much  lighter  liquid  and  having  a  consistency  not 
unlike  that  of  ordinary  water.  The  dilutions  were  continued  with  80 
and  100  gallons  of  water,  but  with  these  amounts  the  solution  was  weak- 
ened to  such  an  extent  that  the  effect  on  the  scales  was  not  satisfactory. 

Difference  in  Amount  of  Caustic  Soda. — The  amount  of  caustic  soda 
in  the  wash  determines  quite  largely  its  effect  upon  the  scale,  since  it  is 
this  ingredient  that  furnishes  the  causticity  of  the  wash.  When  the 
caustic  soda  was  increased  there  was  a  more  marked  shriveling  effect 
produced  on  the  scale,  and  this  could  be  detected  with  the  stronger  solu- 
tion, even  on  the  following  day,  while  with  a  mixture  containing  a 
small  amount  of  caustic  soda  two  or  three  days  elapsed  before  the  same 


SPRAYING    FOR    SCALE    INSECTS.  17 

effect  was  produced.     An  experiment  was  undertaken  to  establish  this 
observation,  with  the  following  result: 

Number        Examined  Examined 

Twigs  Sprayed  March  1st.  of  March  3d.  March  7th. 

Scales.     Per  Cent  Dead.    Per  Cent  Dead. 

With  solution  containing  excess  of  soda 184  73.9  100.0 

With  solution  containing  small  amount  of  soda.  _       214  51.0  87.1 

The  following  table  gives  the  results  of  experiments  with  different 
amounts  of  caustic  soda.  The  twigs  were  sprayed  March  2d  and 
examined  March  10th: 

Amount  of  Caustic  Soda  No.  No.        Per  Cent         No.         Per  Cent 

to  5  gals.  Water—  Scales.        Dead.         Dead.         Alive.  Alive. 

4  pounds 226  226  100.0  0                 0 

3  pounds 180  175  97.2  5                 1.8 

2  pounds 308  302  98.0  6                 2.0 

1  pound 240  220  91.7  20                 8.3 

\  pound 160  132  82.5  28  17.5 

The  Use  of  the  Resin. — While  the  caustic  soda  is  an  important  ingre- 
dient of  the  resin  compound,  the  resin  itself  also  plays  an  important 
part  in  making  the  wash  effective.  It  does  this  in  two  ways:  first,  in 
causing  the  wash  to  adhere  to  the  tree,  and  second,  in  the  impervious 
coating  formed  by  the  resin  itself.  The  efficiency  of  this  wash  as  a 
remedy  for  the  apricot  scale  depends  to  a  large  degree  on  its  ability  to 
adhere  to  the  smaller  twigs  where  the  scales  are  found.  But  the  effect 
of  the  resin  itself  is  also  to  kill  a  number  of  the  scales,  as  was  shown 
in  an  experiment  where  the  resin  alone  was  used. 

The  Use  of  the  Fish  Oil. — The  use  of  the  fish  oil  may  be  compared  to 
the  use  of  the  salt  in  the  lime-sulfur-salt  wash,  in  that  it  is  difficult 
to  demonstrate  just  what  its  function  is.  No  doubt  the  oil  itself  acts 
directly  upon  the  scales  to  a  certain  extent.  This  is  certainly  true  if  a 
sufficient  quantity  is  used,  as  was  shown  in  the  case  of  twigs  that  were 
sprayed  with  a  solution  of  oil  and  water.  In  addition  to  this  direct 
effect  on  the  scales,  it  is  also  useful  in  softening  the  resinous  coating  on 
the  tree,  and  thus  preventing  the  hard,  varnish-like  covering  which 
would  be  formed  by  the  resin  itself. 

Several  substitutes  were  tried  for  the  fish  oil,  and  the  most  promising 
of  these  was  a  distillate.  This  was  a  28°  gravity  oil,  and  it  mixed  with 
the  other  materials  even  better  than  the  fish  oil.  However,  since  the 
effect  of  the  oil  on  the  resinous  coating  is  probably  its  most  important 
function,  this  is  better  brought  about  by  the  heavier  and  less  volatile 
fish  oil.  Crude  oil  was  also  substituted  for  the  fish  oil,  but  the  product 
was  too  coarse.  It  did  not  mix  well,  and  consequently  separated  out 
in  the  spray  tank,  and  was  also  injurious  to  the  tree,  unless  but  a 
small  amount  was  used. 


18  UNIVERSITY    OF   CALIFORNIA — EXPERIMENT   STATION. 

Addition  of  Arsenic. — Experiments  in  the  addition  of  arsenic  to  the 
kerosene  emulsion  and  resin  compound,  carried  on  by  Mr.  Koebele 
several  years  ago,  suggested  the  use  of  arsenic  in  these  experiments, 
but  since  the  resin  compound  itself  proved  satisfactory,  only  a  single 
spray-tankful  of  the  mixture  was  prepared.  A  pound  of  arsenic  was 
used  to  200  gallons  of  the  spray.  The  arsenic  was  prepared  according 
to  the  Kedzie  formula,  as  follows:  The  arsenic  and  4  pounds  of  sal 
soda  were  boiled  in  one  gallon  of  water  for  twenty  minutes.  This, 
together  with  3  or  4  pounds  of  lime,  was  then  added  to  the  resin  solu- 
tion. A  flocculent  precipitate  was  at  once  formed,  which  was  later 
partly  dissolved,  but  much  sediment  still  remained  in  the  bottom  of  the 
spray  tank.  The  trees  treated  with  this  mixture  had  the  appearance 
of  being  dusted  over  with  a  white  powder.  No  difference  was  observed 
in  the  effect  on  the  scale,  but  the  trees  which  were  just  bursting  into 
bloom  appeared  to  show  the  effects  of  the  spray  less  than  that  of  the 
normal  solution,  which  would  indicate  that  the  wash  was  slightly 
weakened,  or  at  least  made  more  neutral  in  its  behavior  toward  the 
petals. 

Effect  of  the  Wash  on  the  Scales. — The  value  of  the  wash  lies  in  its 
caustic  effect  due  to  the  caustic  soda,  which  acts  immediately,  and  also 
to  the  smothering  coating  formed  by  the  resin  and  the  oil.  The  apri- 
cot scale  which  has  been  treated  with  this  wash  first  begins  to  wrinkle 
up  and  turn  pale  in  color  along  the  margin  of  the  body,  leaving  a 
longitudinal  ridge,  which  retains  the  body  fluids  for  some  little  time, 
but  finally  this  also  shrivels  up  and  the  entire  scale  becomes  pale 
brown  in  color.  This  wash  was  very  effective  against  the  apricot  scale, 
and  it  was  rare  that  a  live  scale  was  found  where  the  spray  struck  it. 

On  the  other  hand,  the  resin  wash  did  not  prove  satisfactory  against 
the  San  Jose  scale.  A  pear  tree  that  was  completely  infested  with 
healthy  scales  was  thoroughly  sprayed,  and  on  examination  a  month 
later  quite  a  number  of  live  scales  were  found.  A  laboratory  experi- 
ment gave  somewhat  better  results.  Scales  were  sprayed  March  18th 
and  examined  March  23d: 

Number  of  scales  examined 860 

Number  dead 830 

Number  alive 30 

Per  cent  dead 96.5 

Per  cent  alive. 3.5 

Effect  on  the  Tree. — The  formula  recommended  in  this  bulletin  is  for 
winter  use  on  dormant  trees  only,  and  should  not  be  applied  after  the 
buds  have  begun  to  burst  in  the  spring.  There  seems  to  be  a  period  in 
the  early  spring  when  the  prune  tree  is  very  susceptible  to  the  wash. 
Trees  sprayed  between  February  17th  and  March  1st,  were  not  materially 


SPRAYING    FOR    SCALE    INSECTS.  19 

affected,  while  for  about  two  weeks  following  March  1st,  when  the  fruit 
buds  had  begun  to  swell  perceptibly,  but  no  green  had  yet  appeared,  the 
wash  kept  the  trees  back  almost  two  weeks,  and  many  fruit  buds  were 
killed  outright.  From  that  time  on,  when  the  buds  began  to  unfold 
and  until  the  trees  were  in  full  bloom,  the  wash  had  but  little  effect  on 
the  tree. 

Preparation  of  the  Wash  without  Boiling. — We  are  also  indebted  to 
the  New  York  station  for  a  method  of  preparing  the  wash  without  boil- 
ing by  fire,  but  the  method  in  the  present  experience  was  found  to  be 
rather  unsatisfactory.  The  method  employed  was  as  follows:  Two 
pounds  of  resin  and  one  half  pound  of  caustic  soda  were  placed  in  half 
a  gallon  of  cold  water.  To  this  was  added  one  quart  of  ammonia  (26°), 
and  the  whole  stirred  for  half  an  hour.  The  resin  was  only  partly  dis- 
solved, probably  because  there  was  not  a  sufficient  quantity  of  ammonia; 
but  since  the  cost  was  $1.50  a  gallon,  the  supply  was  naturally  limited. 
More  ammonia  would  probably  dissolve  the  resin,  but  the  cost  and  the 
fact  that  hot  water  is  needed  for  dilution  anyway,  since  the  cold 
solution  does  not  work  well  in  the  nozzles,  make  the  method  impracti- 
cable on  a  commercial  scale,  when  one  half  hour's  boiling  will  bring 
about  the  same  results. 

SUGGESTIONS    FOR    RESIN    SPRAY. 

The  Formula. — The  formula  recommended  in  this  bulletin,  and  which 
was  used  on  the  greater  part  of  the  work  this  season,  differs  from  the 
old  formula  in  having  a  greater  amount  of  water  and  a  less  amount  of 
resin.     It  is  as  follows: 

Resin 10    pounds. 

Caustic  soda  (76%) 3    pounds. 

Fish  oil 1\  pounds. 

Water 50    gallons. 

This  old  formula  seemed  stronger  than  necessary  to  kill  the  scales 
well,  and  besides  its  action  on  the  tree  was  not  so  neutral  as  it  might 
be,  so  that  the  solution  was  weakened  by  the  addition  of  water,  which 
also  effects  a  saving  in  the  cost.  The  effect  of  the  wash  on  the  tree  was 
largely  due  to  the  resin,  and  for  this  reason  the  amount  was  reduced 
somewhat. 

Preparation. — This  wash  is  more  easily  prepared  than  the  lime-sulfur- 
salt  wash,  requiring  less  boiling  and  also  less  attention  to  stirring.  The 
directions  heretofore  given  for  preparing  the  wash  call  for  two  hours' 
boiling,  but  it  was  found  that  there  was  no  advantage  in  boiling  more 
than  half  an  hour.  About  one  half  hour's  boiling  is  necessary  to  dis- 
solve the  resin,  and  this  is  the  object  sought  for,  so  that  further  boiling 
is  a  mere  waste  of  fuel. 


*20  UNIVERSITY    OF    CALIFORNIA — -EXPERIMENT    STATION. 

The  resin  is  broken  up  into  small  lumps,  and  together  with  the 
caustic  soda  is  placed  in  the  boiler  with  three  or  four  inches  of  water. 
The  mixture  should  be  stirred  occasionally  until  the  resin  is  dissolved. 
About  one  fourth  of  the  water  should  be  added,  and  at  the  end  of  a 
half  hour  after  it  has  begun  to  boil  it  is  ready  for  the  spray  tank, 
when  the  rest  of  the  water  is  added.  The  same  apparatus  is  required 
as  that  used  in  the  lime-sulfur-salt  work.  A  stock  solution  may  also 
be  made,  as  suggested  for  this  latter  wash. 

Character  of  Wash. — The  wash  when  ready  for  use  is  a  black-looking 
liquid,  resembling  strong  coffee  in  appearance.  There  is  no  grit  or 
heavy  materials  present,  and  it  sprays  very  readily  through  any  sort 
of  nozzle.  It  does  not  require  stirring  in  the  tank,  unless  a  portion  of 
the  oil  comes  to  the  surface.  Usually  this  amount  is  very  small,  but  if 
there  is  a  quantity  it  should  be  mixed  in  well  with  the  other  materials. 
It  is  soapy  in  character,  but  apparently  not  so  caustic  as  the  lime- 
sulfur-salt  wash,  and  gives  rise  to  no  inconvenience  to  the  hands  and 
face,  except  to  cover  them  over  with  a  sticky  coating.  The  wash  when 
applied  warm  gives  no  trouble  in  the  nozzles;  but  the  precaution 
should  be  taken,  when  through  using  at  night,  to  run  hot  water  through 
them  in  order  to  prevent  the  resin  from  remaining  in  the  parts  of  the 
nozzle  and  hardening. 

Ingredients  and  Cost. — The  resin  comes  in  500-pound  barrels,  pro- 
viding a  quantity  is  purchased,  and  costs  2|  cents  a  pound.  The  caustic 
soda  is  the  commercial  (76%)  soda  used  in  soap  factories,  and  is  sold 
in  100-pound  kegs  or  larger  drums.  Its  cost  is  from  4  to  6  cents  per 
pound,  depending  upon  the  distance  of  transportation.  The  ordinary 
fish  oil  is  used,  and  this  is  put  up  in  5-gallon  cans,  and  costs  40  cents  a 
gallon. 

The  cost  of  the  mixture,  according  to  the  formula  recommended,  is: 

10  pounds  resin,  at  2|  cents $0.27| 

3  pounds  caustic  soda,  at  5  cents .15 

Impounds  fish  oil,  at  5  cents .07$ 

50  gallons  cost $0.50 

1  gallon  costs 0.01 

Application. — Since  the  brown  apricot  scale  is  situated  on  the  under 
side  of  the  smaller  twigs,  the  spray  should  be  applied  from  below,  that 
is,  the  under-shot  spray  should  be  used.  From  their  situation  it  is 
almost  impossible  to  reach  every  scale,  but  spraying  to  the  very  tips 
of  the  twigs  can  not  be  too  strongly  insisted  upon.  It  is  unnecessary 
to  spray  the  trunk  and  larger  branches  for  this  scale,  hence  the  bulk  of 
the  spray  should  be  directed  to  the  smaller  twigs.  In  order  to  reach 
the  scales  on  the  lower  branches,  the  spray  should  be  thrown  at  an 
angle  with  the  axis  of  the  rod,  an  angle  of  about  45  degrees  being  found 
to  be  the  most  satisfactory. 


SPRAYING    FOR    SCALE    INSECTS.  21 


THE    DISTILLATE    SPRAY. 


The  distillate  spray,  a  28°  gravity  oil,  which  finds  a  place  among  the 
remedies  for  scale  insects  in  southern  California,  has  not  been  used  to 
any  extent  on  the  deciduous  trees  of  the  north.  Through  the  courtesy 
of  a  manufacturer  of  spray  pumps,  who  placed  a  power  outfit  in  the 
field,  we  were  able  to  test  in  a  commercial  way  the  value  of  this  spray 
as  a  remedy  for  the  brown  apricot  scale.  The  amount  ordinarily  used 
on  dormant  trees  in  southern  California  is  a  3  per  cent  solution.  This 
has  been  used  there  with  fairly  good  results  against  the  black  scale, 
which  is  similar  in  structure  and  habits  to  the  brown  apricot  scale. 
Working  on  this  basis  we  started  the  experiment  with  a  3  per  cent 
solution,  and  this  was  applied  to  ten  acres  of  prune  trees  that  were 
badly  infested  with  the  scale.  The  result  of  this  work  did  not  come  up 
to  expectations,  and  an  examination  of  several  hundred  scales  gave 
the  amount  killed  as  40  per  cent.  It  was  at  once  evident  that  if  satis- 
factory work  was  to  be  done  by  this  spray,  the  strength  of  the  solution 
must  be  increased,  or  some  other  ingredient  added  that  would  have 
the  required  insecticidal  value. 

Increase  in  Amount  of  Oil. — The  first  test  was  made  with  a  5  per 
cent  solution,  and  the  result  of  this  experiment  was  a  great  improve- 
ment over  the  first,  as  shown  in  the  following  table: 


Solution. 


Total  Number  Number  Number  Per  Cent  Per  Cent 


Scales  Examined.         Alive.  Dead.  Alive.  Dead. 

3  per  cent 1,820  1,092  728  60  40 

5  per  cent 950  95  855  10  90 

The  result  of  this  experiment  seemed  to  indicate  that  if  the  distillate 
was  used  strong  enough  it  would  prove  effective  in  destroying  the 
insects.  This  5  per  cent  solution  had  no  ill  effect  whatever  upon  the 
tree,  and  we  were  only  prevented  from  using  a  still  stronger  solution 
because  of  the  lateness  of  the  season  and  the  fear  of  doing  injury  to 
the  tree,  which  by  this  time  was  bursting  into  bloom. 

Addition  of  Potash. — The  next  series  of  experiments  included  the 
addition  of  potash  in  order  to  strengthen  the  distillate  solution.  For 
this  purpose  ordinary  lye  was  added  to  a  3  per  cent  solution  of  the  oil. 
Different  amounts  of  lye  were  tried,  varying  from  3  to  8  pounds  of  the 
concentrated  98  per  cent  product  to  200  gallons  of  the  3  per  cent  distil- 
late. Each  of  these  mixtures  was  applied  to  a  number  of  different 
trees,  and  at  the  same  time  a  small  experiment  was  carried  on  with  a 
definite  number  of  scales.  The  result  of  these  experiments  was  that 
the  solution  containing  the  greatest  amount  of  potash  proved  very 
effective  on  the  brown  apricot  scale,  and,  indeed,  gave  promise  of  being 
a  very  satisfactory  remedy  for  this  insect.  The  check  experiment  car- 
ried on  in  addition  to  the  field  work  gave,  for  the  total  number  of  scales 


22  UNIVERSITY    OF   CALIFORNIA EXPERIMENT    STATION. 

examined,  94  per  cent  killed.  As  stated  under  the  resin  wash,  the 
caustic  effect  seemed  to  be  an  important  factor  in  control,  and  the 
same  is  true  here.  Both  the  potash  and  caustic  soda  were  used  with 
the  same  result. 

Effect  of  the  Distillate  Spray. — The  action  of  this  spray  on  the  scales  is 
to  cause  them  to  loosen  their  hold  on  the  twig,  and  after  a  few  days  they 
may  be  seen  hanging  by  their  beaks  for  a  time,  when  they  finally  drop 
off  entirely.  In  addition  to  this,  the  shriveling  effect  was  also  noticed, 
and  this  was  particularly  true  on  trees  that  were  treated  with  the 
potash-distillate  spray. 

These  sprays  had  no  injurious  effect  on  the  tree  up  to  the  time  the 
bloom  was  well  out.  About  forty  acres  of  trees  were  sprayed  with  the 
5  per  cent  distillate  when  the  trees  were  in  fall  bloom,  and  they  were 
not  seriously  injured,  although  the  petals  were  badly  browned.  No 
spray,  however,  should  be  applied  as  late  as  this  for  the  apricot  scale. 
This  insect  begins  to  grow  rapidly  after  the  sap  begins  to  come  up  in 
the  tree  in  the  spring,  and  by  the  time  the  tree  is  in  full  bloom  the 
scale  is  of  considerable  size,  and  its  firm  body-covering  renders  it  less 
susceptible  to  the  wash.  No  opportunity  was  given  for  trying  this 
spray  on  the  San  Jose  scale,  and  its  effect  on  this  scale  remains  to  be 
demonstrated. 

SUGGESTIONS   FOR   THE    DISTILLATE    SPRAY. 

While  these  experiments  carried  on  with  the  distillate  sprays  may 
be  considered  as  only  a  beginning,  yet  the  results  seem  to  indicate 
that  there  is  considerable  promise  of  these  solutions  becoming  useful 
as  remedies  for  the  brown  apricot  scale  and  others  of  a  similar  char- 
acter. The  advantage  of  these  sprays  lies  in  the  fact  that  they  are 
less  expensive  than  most  other  sprays,  and  also  in  the  fact  that  they 
require  no  preparation  in  the  way  of  boiling.  They  do,  however, 
require  a  power  outfit  to  apply  them,  since  the  oil  and  water  must  be 
made  into  a  mechanical  mixture  by  violent  agitation. 

The  Formulas. — While  both  the  5  per  cent  distillate  and  the  potash- 
distillate  gave  quite  satisfactory  results,  the  preference  so  far  is  in  favor 
of  the  potash-distillate  spray.  The  formulas  given  below  are  those 
which,  according  to  the  above  experiments,  give  the  most  promise  of 
being  satisfactory.  They  are  given  on  the  basis  of  an  amount  sufficient 
to  fill  the  tank  of  the  power  outfits  in  most  general  use  in  the  State: 

Potash  Distillate. 

Oil. 6  gallons. 

Potash,  or  caustic  soda . 12  pounds. 

Water 200  gallons. 

St  rata  h  t  DUt  Mate. 

Oil .' 10  gallons. 

Water 200  gallons. 


SPRAYING    FOR    SCALE    INSECTS.  23 

The  oil  found  to  be  most  satisfactory  in  southern  California  is  a  28° 
gravity  oil,  specially  refined  for  tree  use.  Its  cost  in  Los  Angeles  is  6 
cents  a  gallon.  To  this,  of  course,  must  be  added  the  freight,  if  bought 
in  other  towns.  The  freight  from  Los  Angeles  to  Hanford  is  about  7 
cents  per  gallon,  making  the  cost  of  the  oil  13  cents  as  delivered  at 
Hanford. 

The  water  and  oil  after  being  made  into  a  mechanical  mixture  have 
the  appearance  of  a  milky  fluid.  It  sprays  very  readily,  and  a  nozzle 
should  be  used  that  will  break  up  the  spray  into  a  fine  mist. 

PATENT    COMPOUNDS. 

The  following  proprietary  compounds  were  tried:  I  X  L,  Fruitolin, 
and  the  Carbolic  spray.  The  last,  which  consists  of  pine  tar  and  car- 
bolic acid,  is  not  a  strictly  proprietary  mixture,  but  will  be  treated 
under  this  head. 

The  I  X  L  Compound. — Opportunity  was  afforded  for  observing  the 
effect  of  the  I  X  L  compound  on  a  large  scale,  as  well  as  for  judging 
of  its  results  on  definite  experiments.  The  conclusion  from  both  of 
these  sources  is  that  the  mixture  has  little  insecticidal  value,  at  least 
so  far  as  the  brown  apricot  scale  is  concerned. 

Marked  twigs  thoroughly  sprayed  with  the  I  X  L  compound  on  March 
1st  and  examined  on  March  10th  gave  the  following  result: 


No.  Scales 

Examined. 

350 

Number 
Dead. 

80 

Number 

Alive. 

275 

Per  Cent 
Dead. 

22.8 

Per  Cent 
Alive. 

77.2 

420 

102 

318 

24.3 

75.7 

/  X  L  and  Resin  Compound  Compared. — A  practical  test  of  the  resin 
wash  and  the  I  X  L  compound  was  made,  as  follows:  Fifty  trees  were 
selected  at  random  from  two  different  orchards  where  no  special  efforts 
were  made  at  applying  the  wash  thoroughly,  and  twigs  from  these  were 
taken  from  various  parts  of  the  tree  and  examined  for  number  of  scales 
killed.  The  trees  were  sprayed  three  weeks  before  the  examination  was 
made,  and  the  result  was  as  follows: 

Compound.  ^Scales 

IX  L 490 

Resin 700 

Most  of  the  twigs  sprayed  with  the  resin  compound  showed  100  per 
cent  killed,  while  a  few  showed  from  90  to  100  per  cent  alive,  indicating 
that  the  twigs  were  not  hit  with  the  spray.  On  the  other  hand,  the 
live  scales  on  most  of  the  twigs  treated  with  the  I  X  L  compound  were 
uniformly  distributed,  while  some  showed  100  per  cent  alive,  indicating 
that  the  wash  was  not  effective. 

Fruitolin. — The  compound  known  as  Fruitolin  is  a  South  American 
product,  and  was  introduced  into  this  State  for  the  first  time  during  the 


Number 

Dead. 

90 

Number 

Alive. 

400 

Per  Cent 

Dead. 

18.3 

Per  Cent 

Alive. 

81.7 

596 

104 

85.2 

14.8 

24  UNIVERSITY   OF   CALIFORNIA EXPERIMENT   STATION. 

present  season.  This  mixture  proved  to  be  quite  effective  on  the  apricot 
scale,  and  it  acts  quickly.  Branches  sprayed  with  Fruitolin  March 
14th  and  examined  March  16th  gave  the  following  result: 

Number  of  scales  counted . 250 

Number  dead 225 

Number  alive 25 

Per  cent  dead 90 

Per  cent  alive 10 

This  wash  is  of  a  soapy  consistency,  and  leaves  a  marked  greasy 
effect  upon  the  tree.  While  the  wash  appears  to  kill  the  scales,  yet  its 
cost,  which  is  20  cents  a  gallon  as  applied  to  the  tree,  makes  it  entirely 
beyond  use  as  a  commercial  spray. 

The  Carbolic  Spray. — This  spray,  which  consists  of  pine  tar  and  car- 
bolic acid,  has  been  used  in  the  State  to  some  extent,  and  some  reports 
claim  it  is  fairly  satisfactory  as  a  remedy  for  the  San  Jose  scale.  The 
present  experience  does  not  bear  this  out  fully,  since  a  number  of  San 
Jose  scales  were  found  alive  on  trees  treated  with  this  wash.  The 
results  of  the  carbolic  spray  on  the  apricot  scale  gave  but  39  per  cent 
killed.  This  application  was  made  a  month  later  than  the  other  com- 
pounds, and  the  scales  had  attained  considerable  size,  so  that  the  wash 
may  be  somewhat  more  effective  than  the  present  results  indicate. 

RESUME. 

The  lime-sulfur-salt  wash  is  an  effective  remedy  for  the  San  Jose 
scale.  It  is  not  satisfactory  for  the  control  of  the  brown  apricot  scale. 
The  old  formula  may  be  reduced  about  one  fourth  without  affecting  the 
results.  The  wash  is  for  winter  use  on  dormant  trees,  and  while  some 
trees  do  not  suffer,  even  if  applied  when  in  full  bloom,  it  is  not  recom- 
mended to  be  used  at  this  time.  The  method  of  boiling  without  fire, 
while  not  reducing  the  cost,  will  prove  useful  under  certain  conditions. 

The  resin  compound  is  a  satisfactory  remedy  for  the  brown  apricot 
scale.  It  is  only  partially  effective  on  the  San  Jose  scale.  It  should 
not  be  used  on  trees  after  the  fruit  buds  begin  to  burst.  The  time  of 
application  for  the  brown  apricot  scale  is  during  the  months  of  January 
and  February,  when  the  scales  are  all  small  and  will  most  readily  suc- 
cumb to  treatment.  The  ammonia  method  of  dissolving  the  resin  is 
not  practicable. 

The  standard  3  per  cent  distillate  failed  to  kill  a  satisfactory  percent- 
age of  the  apricot  scales.  A  5  per  cent  solution,  and  a  3  per  cent  solu- 
tion with  potash  give  promise  of  good  results,  with  the  advantage  in 
favor  of  the  latter. 

The  patent  compounds  have  no  advantage  over  remedies  that  are 
considered  as  standard. 


